WASHINGTON - The armed forces, already struggling to meet recruiting goals, are considering expanding the number of noncitizens in the ranks -- including disputed proposals to open recruiting stations overseas and putting more immigrants on a faster track to U.S. citizenship if they volunteer -- according to Pentagon officials.

Foreign citizens serving in the U.S. military is a highly charged issue, which could expose the Pentagon to criticism that it is essentially using mercenaries to defend the country. Other analysts voice concern that a large contingent of noncitizens under arms could jeopardize national security or reflect badly on Americans' willingness to serve in uniform.

The idea of signing up foreigners who are seeking U.S. citizenship is gaining traction as a way to address a critical need for the Pentagon, while fully absorbing some of the roughly one million immigrants that enter the United States legally each year.

The proposal to induct more noncitizens, which is still largely on the drawing board, has to clear a number of hurdles. So far, the Pentagon has been quiet about specifics -- including who would be eligible to join, where the recruiting stations would be, and what the minimum standards might involve, including English proficiency. In the meantime, the Pentagon and immigration authorities have expanded a program that accelerates citizenship for legal residents who volunteer for the military.

And since Sept. 11, 2001, the number of immigrants in uniform who have become U.S. citizens has increased from 750 in 2001 to almost 4,600 last year, according to military statistics.

With severe manpower strains because of the wars in Iraq and Afghanistan -- and a mandate to expand the overall size of the military -- the Pentagon is under pressure to consider a variety of proposals involving foreign recruits, according to a military affairs analyst.

"It works as a military idea and it works in the context of American immigration," said Thomas Donnelly, a military scholar at the conservative American Enterprise Institute in Washington and a leading proponent of recruiting more foreigners to serve in the military.

As the wars in Iraq and Afghanistan grind on, the Pentagon has warned Congress and the White House that the military is stretched "to the breaking point."

Both President Bush and Robert M. Gates, his new defense secretary, have acknowledged that the total size of the military must be expanded to help alleviate the strain on ground troops, many of whom have been deployed repeatedly in combat theaters.

Bush said last week that he has ordered Gates to come up with a plan for the first significant increase in ground forces since the end of the Cold War. Democrats who are preparing to take control of Congress, meanwhile, promise to make increasing the size of the military one of their top legislative priorities in 2007.

"With today's demands placing such a high strain on our service members, it becomes more crucial than ever that we work to alleviate their burden," said Representative Ike Skelton, a Missouri Democrat who is set to chair the House Armed Services Committee, and who has been calling for a larger Army for more than a decade.

But it would take years and billions of dollars to recruit, train, and equip the 30,000 troops and 5,000 Marines the Pentagon says it needs. And military recruiters, fighting the perception that signing up means a ticket to Baghdad, have had to rely on financial incentives and lower standards to meet their quotas.

That has led Pentagon officials to consider casting a wider net for noncitizens who are already here, said Lieutenant Colonel Bryan Hilferty, an Army spokesman.

Already, the Army and the Immigration and Customs Enforcement division of the Department of Homeland Security have "made it easier for green-card holders who do enlist to get their citizenship," Hilferty said.

Other Army officials, who asked not to be identified, said personnel officials are working with Congress and other parts of the government to test the feasibility of going beyond U.S. borders to recruit Soldiers and Marines.

Currently, Pentagon policy stipulates that only immigrants legally residing in the United States are eligible to enlist. There are currently about 30,000 noncitizens who serve in the U.S. armed forces, making up about 2 percent of the active-duty force, according to statistics from the military and the Council on Foreign Relations. About 100 noncitizens have died in Iraq and Afghanistan.

A recent change in U.S. law, however, gave the Pentagon authority to bring immigrants to the United States if it determines it is vital to national security. So far, the Pentagon has not taken advantage of it, but the calls are growing to take use the new authority.

Indeed, some top military thinkers believe the United States should go as far as targeting foreigners in their native countries.

"It's a little dramatic," said Michael O'Hanlon, a military specialist at the nonpartisan Brookings Institution and another supporter of the proposal. "But if you don't get some new idea how to do this, we will not be able to achieve an increase" in the size of the armed forces.

"We have already done the standard things to recruit new Soldiers, including using more recruiters and new advertising campaigns," O'Hanlon added.

O'Hanlon and others noted that the country has relied before on sizable numbers of noncitizens to serve in the military -- in the Revolutionary War, for example, German and French soldiers served alongside the colonists, and locals were recruited into U.S. ranks to fight insurgents in the Philippines.

Other nations have recruited foreign citizens: In France, the famed Foreign Legion relies on about 8,000 noncitizens; Nepalese soldiers called Gurkhas have fought and died with British Army forces for two centuries; and the Swiss Guard, which protects the Vatican, consists of troops who hail from many nations.

"It is not without historical precedent," said Donnelly, author of a recent book titled "The Army We Need," which advocates for a larger military.

Still, to some military officials and civil rights groups, relying on large number of foreigners to serve in the military is offensive.

The Hispanic rights advocacy group National Council of La Raza has said the plan sends the wrong message that Americans themselves are not willing to sacrifice to defend their country. Officials have also raised concerns that immigrants would be disproportionately sent to the front lines as "cannon fodder" in any conflict.

Some within the Army privately express concern that a big push to recruit noncitizens would smack of "the decline of the American empire," as one Army official who asked not to be identified put it.

Officially, the military remains confident that it can meet recruiting goals -- no matter how large the military is increased -- without having to rely on foreigners.

"The Army can grow to whatever size the nation wants us to grow to," Hilferty said. "National defense is a national challenge, not the Army's challenge."

He pointed out that just 15 years ago, during the Gulf War, the Army had a total of about 730,000 active-duty Soldiers, amounting to about one American in 350 who were serving in the active-duty Army.

"Today, with 300 million Americans and about 500,000 active-duty Soldiers, only about one American in 600 is an active-duty Soldier," he said. "America did then, and we do now, have an all-volunteer force, and I see no reason why America couldn't increase the number of Americans serving."

But Max Boot, a national security specialist at the Council on Foreign Relations, said that the number of noncitizens the armed forces have now is relatively small by historical standards.

"In the 19th century, when the foreign-born population of the United States was much higher, so was the percentage of foreigners serving in the military," Boot wrote in 2005.

"During the Civil War, at least 20 percent of Union Soldiers were immigrants, and many of them had just stepped off the boat before donning a blue uniform. There were even entire units, like the 15th Wisconsin Volunteer Infantry [the Scandinavian Regiment] and General Louis Blenker's German Division, where English was hardly spoken."

"The military would do well today to open its ranks not only to legal immigrants but also to illegal ones and, as important, to untold numbers of young men and women who are not here now but would like to come," Boot added.

"No doubt many would be willing to serve for some set period, in return for one of the world's most precious commodities -- U.S. citizenship. Some might deride those who sign up as mercenaries, but these troops would have significantly different motives than the usual soldier of fortune."